Question: $\dfrac{9}{4} - \dfrac{2}{5} = {?}$
Explanation: $ = {\dfrac{9 \times 5}{4 \times 5}} - {\dfrac{2 \times 4}{5 \times 4}} $ $ = {\dfrac{45}{20}} - {\dfrac{8}{20}} $ $ = \dfrac{{45} - {8}}{20} $ $ = \dfrac{37}{20}$